Johnson is in custody after his arrest and, with police saying he is continuing to help them with their enquiries, the 27-year-old was suspended by the Premier League club pending the outcome of the investigation.
“A 27-year-old man was arrested earlier today on suspicion of sexual activity with a girl under 16,” a Durham police statement said.
“He remains in police custody and is helping officers with their enquiries.”
According to several newspapers, Johnson had sex with a 15-year-old and was arrested at his mansion on Monday morning.
Three unmarked cars, a police van, plain clothes officers and crime scene investigators were reported to have been at the player’s home.
Johnson was due to travel with the rest of the Sunderland squad to Hull for Tuesday’s league match.
But the club’s statement read: “Sunderland AFC has confirmed that Adam Johnson has been suspended from the club, pending the outcome of a police investigation.
“No further comment will be made at the present time.”
Johnson, who has won 12 caps for England, started his career at Middlesbrough before joining Manchester City.
He moved to Sunderland for £10 million ($15 million, 13 million euros) in 2012.